1. Field of the Invention
The present invention relates to a human-collaborative robot system in which a robot and a human share a working space.
2. Description of the Related Art
In contrast to a conventional robot that operates in a working space separated from a working space of a human by a safety fence, in recent years, a human-collaborative robot in which a robot and a human share a working space has been spread. In the human-collaborative robot, it is necessary to ensure safety in order to prevent an injury to a human.
Japanese Laid-open Patent Publication No. 2012-040626A discloses a human-collaborative robot system in which when a detection value of a force sensor installed in a robot or a device mounted in the robot has exceeded a predetermined value, the robot is stopped or a motion of the robot is controlled so as to decrease the detection value of the force sensor.
Japanese Laid-open Patent Publication No. 2010-137312A discloses a robot system which is provided with a collision detection device that detects a collision of a robot arm with an obstacle, and is configured to selectively perform an appropriate stop method such that mechanical damage of a robot and the obstacle is minimally restrained on the basis of information from the collision detection device. In detail, according to the known art, on the basis of information of a relation between a rotation direction of a servo motor and a direction of collision torque, a rotation speed of the servo motor, and the like, a robot is stopped according to one of a sudden stop process, a slow stop process, and an all-axis pullback process.
However, in the known art disclosed in Japanese Laid-open Patent Publication No. 2012-040626A, when a contact between the robot and the human has been detected, the robot always performs a predetermined operation. Therefore, for example, a worker having made contact with the robot may feel threatened by the robot that suddenly stops, and his or her work is disturbed even if there is little risk in fact. In the known art disclosed in Japanese Laid-open Patent Publication No. 2010-137312A in which various stop processes are selectively performed, it is not expected that the robot is stopped in a manner in which a worker having made contact with a robot feels a sense of safety.
In this regard, there is a need for a human-collaborative robot system configured to slowly stop a robot so as to give a sense of safety to a human while ensuring the safety of the robot and a surrounding environment of the robot.